Role of intra-acrosomal antigenic molecules acrin 1 (MN7) and acrin 2 (MC41) in penetration of the zona pellucida in fertilization in mice

Abstract

In this study the role of two intra-acrosomal molecules, acrin 1 (MN7) and acrin 2 (MC41), during in vitro fertilization (IVF) was examined. The pertinent monoclonal antibodies mMN7 and mMC41 specifically recognize a 90 kDa protein (acrin 1) localized to the entire acrosome and a 200 kDa protein (acrin 2) localized to the cortex region of the anterior acrosome, respectively. Experiments were designed to assess the effects of mMN7 and mMC41 on fertilization in mice using TYH medium containing mMN7 or mMC41 at 0.0, 0.025, 0.05 and 0.1 mg ml-1. Under these conditions, capacitated spermatozoa inseminated the cumulus-invested oocytes. Acrosome-reacted spermatozoa inseminated the zona pellucida-free oocytes. The antibodies had no effect on sperm motility and primary binding to the zona pellucida, but significantly inhibited the rate of fertilization of zona pellucida-intact oocytes in a dose-dependent manner. A significantly small number of spermatozoa remained attached to the zona pellucida at 5 h after insemination in the presence of mMC41. mMC41 and mMN7 antibodies did not affect the fertilization rate of zona pellucida-free oocytes. Confocal laser scanning microscopy with indirect immunofluorescence traced the effect of the monoclonal antibodies on the zona pellucida-induced acrosome reaction, and revealed that mMN7 prevented completion of acrosomal matrix dispersal, whereas mMC41 did not affect the acrosome reaction. mMC41 appeared to inhibit secondary binding or some biochemical steps on the zona pellucida after the acrosome reaction but before penetration of the zona pellucida. Thus, the intra-acrosomal antigenic molecules acrin 1 and acrin 2 are essential for distinct events before sperm penetration of the zona pellucida in mice.

Changes in distribution and molecular weight of the acrosomal protein acrin2 (MC41) during guinea pig spermiogenesis and epididymal maturation

“…It has been also suggested that some OAM/matrix-associated glycoproteins may serve to hold vesiculated plasma and outer acrosomal membranes together during the acrosome reaction (Yanagimachi 1994). Furthermore, our recent in vitro study has shown that the MC41 antibody affects the secondary binding or inhibits the maintenance of tight binding of mouse sperm to the zona pellucida, suggesting a significant role of acrin2 in sperm-zona interaction (Saxena et al 1999). …”

“…More recently, acrin2 was shown to be released while staying in close contact with the vesiculated membrane during the acrosome reaction, suggesting that it may function in sperm-zona pellucida interaction during fertilization (Tanii et al 1995;Saxena et al 1999). In the present study, our aim was to define the behavior of acrin2 during the development and maturation of the guinea pig sperm acrosome.…”

Biology of spermatozoa maturation: An overview with an introduction to this issue

“…It has also been clarified that the acrosome contains not only hydrolytic enzymes but varieties of functional molecules required for the complex steps of sperm-egg interaction as well, including binding to the zona pellucida, induction of the acrosome reaction, and penetration through the zona (Saxena et al, 1999(Saxena et al, , 2000Kim et al, 2001). To execute these modifications that culminate in the acrosome reaction, these acrosomal proteins are initially compartmentalized into the nascent acrosome in developing spermatids and then undergo maturation, structure remodeling, and the redistribution of the proteins to the most appropriate site in the maturing spermatozoa (Toshimori et al, 1995;Tulsiani et al, 1998a;Yoshinaga et al, 2000).…”

Organization and modifications of sperm acrosomal molecules during spermatogenesis and epididymal maturation

“…The acrosome of the mouse has two domains, the cortex and medulla: acrin2 and acrin3 (MC101), a 155 kDa protein, are localized in the cortex, while acrin1 is distributed over the entire anterior acrosome Toshimori et al, 1995). Such segregation may reflect functional differences in the intra-acrosomal proteins: acrin1 may aid in the completion of the acrosome reaction, while acrin2 may play a role in secondary binding to the zona pellucida after the acrosome reaction (Saxena et al, 1999;Tanii et al, 2001). Acrin3 appears to participate in zona pellucida penetration (Saxena et al, 2000).…”